Saturated phospholipids in amniotic fluid of normal and diabetic pregnancies

To assess fetal lung maturation in normal and diabetic pregnancies, the authors studied two phospholipids that are more specific for pulmonary surfactant than total phosphatidylcholine (lecithin), namely saturated phosphatidylcholine and phosphatidylglycerol. Results indicated that saturated phosphatidylcholine concentrations normally increase from 10 to 20 nmol/mL before 34 weeks to as high as 150 nmol/mL at term. Although the absolute concentration of saturated phosphatidylcholine could not be used to reliably identify pregnancies leading to respiratory distress syndrome, a saturated phosphatidylcholine level greater than 50% of total phosphatidylcholine was associated with satisfactory neonatal pulmonary function, whereas RDS often occurred in premature infants when less than half the phosphatidylcholine was saturated. Carefully regulated diabetic pregnancies at 36 to 42 weeks of gestation were not different from matched control subjects with respect to total phosphatidylcholine, its ratio to sphingomyelin, saturated phosphatidylcholine, or phosphatidylglycerol. Respiratory distress syndrome did not occur in any infant of the 40 diabetic mothers studied, nor were there any congenital anomalies or cases of symptomatic hypoglycemia.